1. Field of the Invention
The present invention relates generally to a multiple printing apparatus. More specifically, the invention relates to a multiple printing apparatus which can perform overlapping printing.
2. Description of the Related Art
It has been widely spread in manufacturing plants and so forth to attach labels with printed bar code or so forth on parts for mechanical or visual identification. Nowadays, there are needs for coloring of the labels for easier identification. Also, there is a trend to develop mechanical color recognition apparatus to increase density of label information.
However, in order to cope with such coloring of the labels, it becomes necessary to separate ink ribbons as printing mediums into respective colors and to control shifting of these ink ribbons so as to register the label as a printing object at a desired color position for printing. This inevitably makes a shift control mechanism complicate. Also, when a multi-color printing or color overlapping is required, it becomes necessary to perform printing with reciprocally shifting the printing object to make the shift control mechanism further complicate and to require long period for printing.
It may be a solution for such problem to arrange printing apparatuses in multi-stage for printing different colors in different printing apparatuses. However, in such case, cost for facility becomes significantly high and the length of line of the printing apparatus becomes too long.